In general, a conveyor is any of various devices that provide mechanized movement of material. Conveyors are customarily employed in industrial applications, farms, warehousing, freight handling, mail handling, equipment handling, and mines. Conveyors can be a few inches in length, or several miles long. A variety of conveyors are currently available and widely employed in various industries.
Gravity-roller conveyors consist of a series of parallel rollers fastened to a metal frame supported at intervals. The frame can be inclined for gravity flow.
Floor conveyors use chain, cable, or other linkage mounted proximate to the floor in an endless track. Floor conveyors are customarily designed to drag a train of wheeled carts in a loop to carry large items for assembly on the conveying system.
Slat conveyors employ endless chains, driven by electric motors operating through reduction gears and sprockets, with attached spaced slats to carry objects that would damage a belt because of sharp edges or heavy weights.
Flight conveyors have scrapers, or flights, mounted at intervals perpendicular to the direction of travel on endless power-driven chains operating within a trough. Flight conveyors are useful for conveying bulk materials such as sawdust, sand, gravel, coal, and chemicals.
Apron conveyors consist of endless chains having attached overlapping and interlocking plates to provide a continuous-carrying surface. The continuous-carrying surface forms a leakproof bed suitable for bulk materials without containers.
Vibrating conveyors include troughs or tubes flexibly supported and vibrated by mechanical or electrical means to convey objects or bulk material. The vibration causes directional and inclined movement of the material.
In trolley conveyors an overhead rail carries a series of load-bearing trolleys coupled together on an endless propelling medium, such as cable, chain, or other linkage. The trolleys vary in design dependent upon the load to be handled, and are customarily employed within plant buildings. The rail is usually supported by a framework of the plant building.
En masse conveyors use skeletal or solid flights mounted at intervals on a cable or chain power driven within a closely fitting casing. En masse conveyors are designed for bulk materials that must be enclosed to prevent leakage or explosion.
Bucket conveyors consist of buckets attached to endless chains or belts. The buckets remain in carrying position until they are tipped to discharge the material.
Screw conveyors incorporate revolving shafts with continuous or broken spiral flighting that operates inside a casing. The screw conveyor customarily operates in one direction to move fine bulk material, such as meal, seed, and coal.
In addition to the above conveyors, the most common conveyor is the belt conveyor. A belt conveyor incorporates a belt of fabric, rubber, plastic, leather, or metal. The belt is endless to form a continuous loop, and is the carrying medium. The belt is looped around rotating rollers at either end of the conveyor. At least one of the rollers is powered to rotate the belt about the rollers. The belt is pulled over beds of unpowered, rotating idler rollers between either end of the conveyor. The beds of idler rollers allow weight to be conveyed as they reduce the amount of friction generated from heavy loads on the belt. Electric motors operating through constant- or variable-speed reduction gears usually provide the power to the drive or powered roller.
Belt conveyors are the most commonly used powered conveyors because they are versatile and cost effective. Product is conveyed directly on the belt enabling the transport of regular and irregular shaped objects, large or small, light and heavy, and bulk material. These conveyors should use only the highest quality premium belting products, which reduces belt stretch and results in less maintenance for tension adjustments.
There are two main industrial classes of belt conveyors: general material handling and bulk material handling. General material handing belt conveyors are used to move letters, boxes, packages, and the like inside a factory or distribution center. Bulk material handling belt conveyors are used to transport large volumes of heavy, abrasive, and granular material, including grain, grain, salt, coal, ore, sand, overburden, and more.
Belts used in bulk material handling belt conveyors are strong, rugged, and durable. Belts customarily have three layers: a top cover, a carcass, and a bottom cover. The carcass provides linear strength and shape, and is often a woven or metal fabric having a warp & weft, the warp being longitudinal cords having resistance and elasticity that define the desired running properties of the belt, and the weft being the transversal cables to give the belt specific resistance against cuts, tears, and impacts and at the same time high flexibility. Common carcass materials are steel, polyester, nylon, cotton and aramid. The covers are usually various rubber or plastic compounds specified by use of the belt.
The rollers of belt conveyors are inherently susceptible to frictional wear from the moving belt. This is especially the case with bulk material handling belt conveyors used in mines, agriculture, and other environments where abrasive dust, earth or other matter in fine, dry particles, between the rollers and the belt increases the friction between the rollers and the belt that transports the large volumes of material. Thinning of a roller of a belt conveyor resulting from excess wear can cause it to crack, splinter, and fail, which can lead to costly, unscheduled downtime to repair the failed roller, a more prolonged and costlier unscheduled downtime when the failed roller damages the belt or other equipment, and injury or death to workman working near the conveyor.